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Topic: Non slipping bend in Dyneema (Read 67044 times)

I have a bend that does hold - it's a modification of the blood knot (pictures here:http://www.bethandevans.com/pdf/bend.pdf). It is a bit more complex than is ideal, but it is "low profile", and is the only bend I have tested that does not slip.

It is 100% in 'loop configuration' (as I was reporting all the other bend numbers - not sure if I made that clear), so 50% as a straight knot (that's two pulls). I think 50% is roughly as good as it gets in dyneema.

There are two slightly different ways to tuck the tails back - one way they slip at about the same loads as the triple fisherman, and the other way they hold, and unfortunately I am not sure which way I photographed. I will have to do some checking tomorrow.

Also, two Estar's might be quicker and easier to tie than this, and we know they don't slip and are strong and low profile

Estar just indicated that he has been testing loops so it seems like my knot is not 68% but rather 34% as it is only taking half the force because of the loop. The blood knot above is 100% or 50% on the knot. I have asked for clarification but wanted to alert any readers here that the strength has most likely been overstated.

You should get some of this line and try and tie a knot in it and see if it slips. I think it would be useful for you to understand how slippery it is. I will send you some if you like.

I have already shown the Strangle bend ( http://igkt.net/sm/index.php?topic=4756.msg30732#msg30732 ) - so we go one only step beyond the Fisherman s knots. I try to compare smaller apples to larger apples - this is why I had made this suggestion. Next, one more step further from this, where the wraps are interweaved a little more, is the also very simple and easy to tie Trefoil bend, shown at the attached pictures. Test them, and then we will see. I will not present you some really big guns we have - we will use them later. The true reason is that I try to figure out the Achilles" tendon of this material... By comparing results of tests on similar bends, I believe will gradually be able to understand more things.

There are members of this Forum who have used Dyneema ropes, and know some things about knots tied on this material. Personally, the only thing I know for sure is that the recommendations for the use of the triple Fisherman s knot are quite common - I believed until now that this bend was extensively tested on exactly the material you cite. I have even tried to guess some more convoluted bends that could serve as substitutes of the triple fisherman s knot - and, to read my hand-weaving, vague arguments ( in the absence of a test rig, I could nt do anything else...), and get an idea of some big guns, see :

I have completed some testing using a 500 pound test version of this line called "Lash It" I am able to make loops with that so that I can pull hard enough to cause the knot I submitted to slip. When I used figure of eight loops to terminate my knot, the figure of eight knots would break before my knot slipped. The funny thing is that when it slipped, a puff of smoke came out of the knot!. I then made a loop with the trefoil knot and interlaced with a loop with my knot. Kind of a tractor pull to find the strongest knot. The trefoil slipped without any noticeable slippage on my knot.

Estar tested the above knot and in his test, unlike mine, it slipped ...

Before my sleepy eyes fail fully,IIRC of EStar's on-line documentation,his supposedzeppelin bend was NOT that,{{edit to correct: EStar has it right, at www.bethandevans.com/load.htm so, "sleepy eyes" was seeing things! But awake eyes now sees there the "tails opposite" version of the sheet bend, which is generally regarded as the inferior version --tails should be on same side. So, its slippage in this version is less a surprise. Also, I'd never orient the butterfly like that; a better orientation should see higher values.}}but a sadly too common misrepresentationof it. The initial structures of the two endsshould form what can be seen as "p & d"not "p & b" --the draw on the loaded endswill rotate the nipping turns in the samedirection, not opposite.

NB: the butterfly eye knot is asymmetric,so testing of that should indicate which end is beingloaded; and the dressing of the knot as I see itmost often is not what I'd expect to get morestrength (but I must admit that the good strengthit sometimes gets, thus, doesn't leave much roomfor improvement!). In forming the eye knot bywhat has been jocularly called "the twirly flop"method, there is a natural tendency by torsionfor the eye legs to cross in their exitingof the knot, not be pressed against each otherin a plane including the axis of tension.(In introducing this knot to climbers back in 1928,Wright & Magowan specifically pointed out thiscrossing as desired; I don't recall that they hada testing basis for so desiring, but maybe justa sort of "go with the flow" pointer, to say "yes,it should go like this".)

As for slippage of the double grapevine (a nameI favor for it better matches to parts of the knot--the "double", i.e.), Xarax's alarm should be amelioratedby realization that those who make the recommendationfor its use do so on the basis of their testing thematerial in which it's recommended to be tied--i.p., HMPE-cored, polyester-sheathed small cord.And they have break tests of that, not slippage.YMMV, again.(I sure would like to see video of it slipping,though, as seen for the dbl.bowline "#1"!)

I have a bend that does hold - it's a modification of the blood knot(pictures here:http://www.bethandevans.com/pdf/bend.pdf).

NB: what you show (as do many others, I know)is not a blood knot, really, unless you getthose turns to capsize into wraps around straightS.Parts (i.e., the loaded ends)! This is sadly somethinglost to the knot-parroters who've seen such imagesin fishing-knots books and taken them into ropeand ... the transformation might not occur.It's a distinction of what Barnes called "in-coil"& "out-coil"; in nylon fishing line, upon setting,the result is the same --in-coil. (And, surprisingly,there is enough force transmitted into the wrapsto leave indentation impressions on the S.Parts,with break coming at the center of the knotwhere the tails caused a deflection --and notat the hard (1-diameter) turns of the S.Partswhere they turn back & wrap!)

I suggest that you endeavor to get this arrangementin the HMPE line, perhaps must adding a 2nd tuckingof the tails, for security?

You've essentially tied extended anchor/fisherman bendsof each end around the other.

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It is 100% in 'loop configuration' ..., so 50% as a straight knot (that's two pulls).

I take it that you are making a statement ofequality here, not reporting separate test results?Beware this apparent (logical!) equality, as it mightbe more the case that the naive adding of the 100%side and the whatever-% knotted side is more tothe truth of closed-loop sling strength, practically--the point being that with knot compression thatside will lengthen and lighten its load, and equalizationaround the pins or whatever is pulling the sling apartmight be inefficient and so indeed the unknotted sidecould shoulder a bigger portion of the load, and bothsides reach their resp. maximums, say 100% + 60% !(I believe I've read reports where the break came atthe pins, not at the knot, too.)

I can only test one thing against another so that is what I do. I am using smaller line now but not mixing results, all results I give of one vs another are in the same size line. I am not picking line for any other reason than this is what I can test. That said, I tested my knot against the four knots here http://igkt.net/sm/index.php?topic=3668 and mine is in the middle. The first two knots slipped first but in the second two, mine slipped. I did not test the last two against each other as I find them just too hard to tie to be practical on a boat.

PS. This is a reply to post #29. Sorry, I am not familiar with how your forum works.

I am a bit less enthused about the modified blood knot this morning - I have tested 12 pulls, and it slips (at about the triple fisherman slip load) in about 1/3 of them (that may or may not be due to the capsize issue mentioned above). Practically speaking it will be easier and more secure (and equally compact) to tie two EStar loops, so for now that is the best solution I have found.

As to those suggesting we look at 'simpler' bends . . . I would love to find one that works . . . but I have now tested quite a few and just can't see how we are going to find one "simpler' than (for example) the triple fisherman that will work. The EStar is the "simplest" knot I have found that holds securely in this stuff. It is my benchmark for now.

The EStar tests at 50%. The only thing I have tested higher is the Polamar at 54% (Just barely statistically significantly stronger). But you cannot (easily) tie the Polamar as a bend.

For those questioning the triple fisherman slipping. I have a series of photos below. #1 is no load, #2 is 1300lbs of load after it is all tightened up and the tails start slipping (I put some new black marks on the tails at this point to watch them being sucked into the knot), and #3 has one of the tails almost into the knot. It does this every-time, consistently.

the Strangle bend - shown in the attached pictures - , because the wraps of the one link squeeze the ones of the other. Could you, please, try to pull this bend - because I am dying out of curiosity ! Of course, I suppose you would set and pre-tighen the bends a little bid, before the final loading.

Diamond bend slips against my bend. It also took me 15 minutes to figure out how to tie it. I must say that this class of knots, at least with just trying to tie it by following these pictures, could never be tied on a moving boat at sea. Perhaps there is an easier way but as they slip against a very easy to tie knot there really isn't a point. That, of course, does not apply to the two knots that did not slip against my knot so if there is an easy way to tie those two I would love to know what it is.

Those knots are complex in their form, but simple in their tying - and, as symmetric, instantly inspected. The idea was to re-trace the path of a symmetric stopper. Just tie the stopper, as the one link of the bend, on the end of the one line, and retrace its path, without any further thinking, with the end of the other the opposite way - that is, just follow what the first line had followed as it closed in itself.

That is how I tied them. I call them retrace knots, like a water knot. It is probably harder with the line I am using which is very small.

I still find this category of knot difficult to tie. The benchmark is a bowline, which I just tied one handed behind my back without looking. The bend I proposed takes two hands so it isn't as easy as a bowline. But you need to be able to tie a knot in your shower standing on one of those exercise balls with the water on of course :-)

I am a bit less enthused about the modified blood knot this morning--I have tested 12 pulls, and it slips (at about the triple fisherman slip load)in about 1/3 of them(that may or may not be due to the capsize issue mentioned above).

What I mentioned about "capsizing" / transformingcannot occur in your knot with its tucked tails;rather, it should occur --a design goal, i.e.--for the blood knot, and hence my suggestionfor revision (tie "in-coil" (working end wrapping backover the overlapped S.Parts to the center tuckingpoint), and make an extra tuck in hopes of locking).

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For those questioning the triple fisherman slipping.

NB : what you show here is the triple grapevine hencequadruple fisherman's knot ! (And we can seewhy I favor the former name --it matches the visiblewraps (triple ; a (single) fisherman's knot has none,not one). The pre-loaded knot looks as though it couldbe better tightened? Still, the slippage is so eye-opening,knots-thinking-shattering!! Thanks.

Note that the tails of these knots could be takenthrough their opposite halves; I've no idea if thiswould enhance security. It certainly would complicatetying the knot, as one cannot form one half and thenthe other, as this novel tail-tucking needs part of the"other half" to be formed, into which to tuck.

Let me suggest a relatively "simple" knot --the baseis the overhand : Ashley's #1452, sometimes presentedas Ashley's bend. I'll ask that it be tried, as is,and then with the simple securing measure of puttingin a 2nd course of tails tucking --which bulks its centralturning-around mass to four diameters, and putsdouble collars against the SParts' entry.((Sorry, don't have a good image for that in 100kbor less, so let's look at the similar Ashley's #1408.))

I can't imagine this slipping (to become untied ; slippingto generate heat on rapid loading and ... , maybe);but then I couldn't imagine a multiple grapevineslipping, either (or the rope flowing out of a dbl.bwlfrom collapsing the eye!).

From the original knot shown in the attached photo,just take each tail and *trace* the finish of theopposite tail --e.g., the white tail will turn clockwiseand lie atop the yellow tail in making the 2nd tuck;the yellow will reciprocate, running counterclockwisebehind the white tail's initial tuck & exit. (And thisextension --the 2nd tucking-- can be tweaked totry to work out the best version, if it looks fruitful.)

Thank you. You keep testing everything against your knot, and not against each other, and doing so you deprive us from valuable information

I tested the two knots that made mine slip against each other. I made a loop of each knot and larks head knotted the two loops together. It broke at the larks head. I was not going to re-tie those things so did not report it.

I tested the strangle against whatever knot you asked me to. One of the knots suddenly exploded and the test piece fell. I am reasonably sure the strangle survived but not 100% so again I did not report this.

These knots are pretty hard to tie and not suitable for sailing imho so my motivation to do multiple tests when I screw up is limited.